PROJECT SUMMARY/ABSTRACT Pancreatic neuroendocrine tumors (PNETs) are a rare type of cancer that originate in the islets of Langerhans, where important hormones including glucagon, insulin, and somatostatin are produced. These tumors are extremely small and have a variety of general symptoms. Most cases of PNETs are diagnosed when they are in the later stages of development because of this difficulty of detection. Current chemotherapeutic agents lack any real degree of potency in treating PNETs because of complex functions and compositions of pancreas, which prevents specific targeting and delivery of therapeutics. Therefore, surgical resection remains the mainstay of treatment; however, visualization of tumors during operation has been a major challenge. Our hypothesis is that multifunctional nanoprobes, that target PNETs with near-infrared (NIR) fluorescence and radioimaging, will provide sensitive, specific, and real-time image-guidance for early diagnosis and improved therapeutic interventions, including targeted chemotherapy and image-guided tumor resection. The specific aims of this study are focused on developing multifunctional nanoprobes which will enable the targeting, imaging, and image-guided intervention of PNETs; the evaluation of the cellular mechanism and biodistribution of the targeted nanoprobes; and the translation of the tumor-specific nanoprobes for image-guided interventions including chemotherapy and image-guided surgery. The impact of this study will be the creation of an innovative concept to confront the lack of diagnostic systems for early stage PNETs, and the creation of a therapeutic effect through the systemic delivery of therapeutic drugs to the pancreas. When used with an appropriate intraoperative imaging system, NIR fluorescent light from 650 to 900 nm can provide surgeons with real-time localization of normal and diseased tissue, without changing the look of the surgical field. The intraoperative imaging system provides real-time imaging of surgical anatomy (i.e., color video) and two independent channels of NIR fluorescent light (700 nm and 800 nm emission). One NIR channel is typically reserved for a target tissue (e.g., tumor) while the other is reserved for vital tissue that needs to be avoided (e.g., nerves, blood vessels, lymph nodes, etc.). NIR fluorescence, paired with this instrumentation and targeted contrast agents, provides interference-free imaging by avoiding biomolecular autofluorescence and nonspecific organ uptake in the living organism.!The focus of this application is on the development of multifunctional nanoprobes, because the NIR imaging system and a PNET-targeted small molecule inhibitor are already available for preclinical studies. We describe the systematic optimization of chemical composition, including surface charge, systemic delivery, tumor retention, and clearance for targeted nanoprobes through the use of in vitro and in vivo bioassays and bioimaging, as well as preclinical validation in large animals. This will set the stage for rapid clinical translation of these nanoprobes in the future.